JSFiddle - React, Tailwind, and code Playground

HTML

<canvas></canvas>

JavaScript

var cv = document.querySelector('canvas');
var ctx = cv.getContext('2d');

var imgData = ctx.getImageData(0, 0, 1, 1);
//alert([].join.call(imgData.data, ', '));

imgData.data[0] = 224;
imgData.data[1] = 128;
imgData.data[2] = 64;
imgData.data[3] = 102;

ctx.putImageData(imgData, 0, 0);

var imgData2 = ctx.getImageData(0, 0, 1, 1);

alert([].join.call(imgData2.data, ', '));